OS (Operating System) running on a server operating in progress is made to run on another server (which will hereinafter be also termed “an active migration”) without suspending the OS, which facilitates operation management of the server.
The active migration of the server is enabled between virtual servers with hypervisors to control execution of a plurality of different virtualized OSs. This is because the virtual servers cause CPUs to execute instructions via the hypervisors, and a cooperation between the hypervisors of a migration originating server and a migrating destination server enables the migrating destination server to acquire control information of the processor of the migration originating server and to re-run the OS.
On the other hand, such a case exists that a plurality of physical servers is migrated to and integrated into one server as virtual servers for reducing power consumption. With an advent of power-saving CPUs, the servers are operated with the power consumptions proportional to load states. A shift to a new server mounted with the power-saving CPU is expected to increase. The server mounted with the power-saving CPU does not run a plurality of virtual servers on one single server for avoiding futility of the power consumption, and the migration to a physical server from the virtual server is also expected to increase.    [Patent document 1] Japanese Laid-Open Patent Publication No. 2009-145931    [Patent document 2] Japanese Laid-Open Patent Publication No. 2013-205946    [Patent document 3] Japanese Laid-Open Patent Publication No. 2012-74090    [Patent document 4] Japanese Laid-Open Patent Publication No. 2012-234564